Method for remediation of aquifers

ABSTRACT

A method for remediating aquifers and groundwater contaminated, for example, by toxic halogenated organic compounds, certain inorganic compounds, and oxidized heavy metals and radionuclides, using the introduction of an innocuous oil, preferably an edible, food grade oil such as soybean oil, formulated into a microemulsion preferably by mixing with a natural food-grade emulsifier (such as lecithin) and water.

NOTICE: More than one reissue application has been filed for the reissueof U.S. Pat. No. 6,398,960. The reissue applications are Ser. No.10/862,126 and the present application, which is a continuation ofreissue application Ser. No. 10/862,126.

GOVERNMENT LICENSE RIGHTS

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of contractF41624-99-C-8033 awarded by the United States Air Force MaterialCommand.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the remediation of contaminated groundwater,and in particular, relates to a remediation method utilizing amicroemulsion of an innocuous oil.

2. Description of the Related Art

There are numerous techniques employed for the remediation ofcontaminated groundwater in aquifers. The mechanisms for cleanup may bephysical, chemical or biological. A typical physical remediation methodfor groundwater contaminated with volatile solvents includes recovery ofthe contaminated water using a series of wells followed by above-groundtreatment by air stripping and/or activated carbon adsorption.

The most common approach for enhancing the anaerobic conversion oforganic and inorganic contaminants in the subsurface involvescontinuously flushing a soluble readily biodegradable substrate such aslactate or molasses through the contaminated zone. There is, however,significant capital expense associated with the installation of therequired tanks, pumps, mixers, injection and pumping wells and processcontrols required to continuously feed a soluble easily degradablesubstrate. Operation and maintenance costs can be high because of thefrequent clogging of injection wells and the labor required forextensive monitoring and process control.

Treatment of contaminated groundwater in situ is often a less expensiveapproach for groundwater remediation. In situ treatment technologiesgenerally rely on the natural migration of contaminated groundwater tothe treatment zone where the transformation can occur via eitherchemical or biological mechanisms. Most previous in situ bioremediationapproaches have also relied on the injection of oxygen oroxygen-containing chemicals into the aquifer to provide electronacceptors to enhance aerobic biodegradation processes, however, thisapproach is not applicable to chlorinated solvents and other oxidizedcompounds.

In many aquifers, the cleanup rate is controlled by the rate ofcontaminant dissolution and transport by the mobile groundwater. Whendense non-aqueous phase liquids such as halogenated aliphatic organicsolvents are present or contaminants are present in lower permeablezones, dissolution rates are slow and a long time is required foraquifer cleanup. Under these conditions high operation and maintenancecosts are a major problem.

Impermeable barriers are used to restrict the movement of contaminantplumes in ground water. Such barriers are typically constructed ofhighly impermeable emplacements of materials such as grouts, slurries,or sheet pilings to form a subsurface wall. When successful, thesebarriers eliminate the possibility that a contaminant plume can movetoward and endanger sensitive receptors such as drinking water wells ordischarge into surface waters. However contaminated groundwater oftenbypasses around these barriers unless they are constructed to completelyenclose the contamination source.

Technologies to improve the chances that contaminated groundwater willencounter subsurface reactive agents have been developed. One suchtechnique is the permeable reactive barrier (PRB), which is a passive insitu treatment zone of reactive material that degrades or immobilizescontaminants as groundwater flows though it. In contrast to subsurfacewalls, permeable reactive barrier walls do not constrain plumemigration, but act as preferential conduits for contaminated groundwaterflow. In a PRB, reactive materials are placed where a contaminant plumemust move through it as it flows, with treated water exiting on theother side.

PRBs are installed as permanent or semi-permanent replaceable unitsacross the flow path of a contaminant plume. Natural gradients transportcontaminants through strategically placed treatment media. The mediadegrade, sorb, precipitate or remove chlorinated solvents, metals,radionuclides, and other pollutants. These barriers may containreactants for degrading volatile organics, chelators for immobilizingmetals, nutrients and oxygen to enhance bioremediation, or other agents.

The choice of reactive media for PRBs is based on the specific organicor inorganic contaminants to be remediated. Most PRBs installed to dateuse zero-valent iron (Fe⁰) as the reactive media for convertingcontaminants to non-toxic or immobile species. For example, Fe⁰ (canreductively dehalogenate hydrocarbons, such as by converting TCE toethene, and can reductively precipitate anions and oxyanions, such as byconverting soluble Cr⁺⁶ oxides to insoluble Cr⁺³ hydroxides. Thesebarriers consist of a long trench constructed perpendicular to thegroundwater flow that is backfilled with ground-up iron. As thechlorinated solvent and other contaminants flow through the barrier,they react with the iron and are transformed. The transformationreactions that take place in the barriers are dependent on parameterssuch as pH, oxidation/reduction potential, concentrations of thesubstrate(s) and contaminant(s) and reaction kinetics within thebarrier. The hydrogeologic setting at the site is also critical, becausegeologic materials must be relatively conductive and a relativelyshallow aquitard must be present to contain the system. The technologyworks well but is very expensive to construct. Examples include the workof Gillham et al. (1995, unpublished Communication to the InternationalContainment Technology Workshop, Permeable Barriers Session, Baltimore,Md.). The disclosures of all patents and publications referred to hereinare incorporated herein by reference.

Most PRBs are installed in one of two basic configurations:funnel-and-gate or continuous trench, although other techniques usinghydrofracturing and driving mandrels are also used. The funnel-and-gatesystem employs impermeable walls to direct the contaminant plume througha gate, or treatment zone, containing the reactive media. A continuoustrench may also be installed across the entire path of the plume and isfilled with reactive media.

Pump-and-treat technologies and funnel and gate barriers are notconducive to broad site cleanup. These are interceptor technologies;there are no cost-effective technologies that address the entirety ofthe plume in situ.

Remediation techniques that have been employed for various contaminantsare discussed more specifically below. Enhanced anaerobic bioremediationthrough reductive dehalogenation of halogenated aliphatic organic andinorganic compounds has been demonstrated as a method for remediatingaquifers contaminated with chlorinated solvents (Holliger, 1995. CurrentOpinion in Biotechnol. 6:347-51; Beeman et al., 1994. In Bioremediationof Chlorinated and Polycyclic Aromatic Hydrocarbon Compounds, ed.Hinchee, et al., S K Ong, p. 14-27. Boca Raton: Lewis Publishers Elliset al., 2000. Environmental Science and Technology. 34: 2254-2260). Inthis process an organic substrate is emplaced into the aquifer tostimulate the growth of anaerobic dechlorinating bacteria by providingan electron donor for energy generation and carbon source for cellgrowth (Lee et al., 1997, J. Ind. Microbiol. Biotechnol. 18(2/3):106-15;McCarty et al., 1994. Handbook of Bioremediation, Lewis Pub., BocaRaton, Fla., pp. 87-116). For example, tetrachloroethene (PCE) andtrichloroethene (TCE) can be treated by the following reaction:PCE->TCE->cis DCE >VC->etheneCis-dichloroethene (cis-DCE) and vinyl chloride (VC) are produced asintermediate compounds by this reaction. However, when a suitablemicrobial population is present, cis-DCE and VC are completely degradedto the non-toxic end product ethene.

Perchlorate can be biodegraded to chloride under anaerobic conditionsthrough the sequence:ClO₄ ⁻(perchlorate)→ClO₃ ⁻(chlorate)→ClO₂ ⁻(chlorite)→Cl⁻(chloride)This process requires the addition of an organic substrate to removedissolved oxygen, which can inhibit this process, and provide reducingequivalents to drive the reaction. (Herman et al., 1998. Journal ofEnvironmental Quality, 27: 750-754). Studies on perchlorate degradationare primarily laboratory scale. Full-scale applications have beenlimited to treatment of wastewaters generated from handling rocketpropellants in industrial situations.

A variety of inorganic compounds including chromium (Cr), uranium (U)and technetium (Tc) are more mobile in subsurface environments in a moreoxidized state. By promoting anaerobic, reducing conditions, thesecompounds can be converted to a more reduced, less mobile state thatwill promote their immobilization. For example, chromium commonly occursin two oxidation states in the environment: Cr[III] and Cr[VI]. Theoxidized form, Cr[VI], is relatively mobile in the subsurface existingin solution as the HCrO₄ ⁻ and CrO₄ ⁻² ions. The reduced form, Cr[III],is essentially immobile in ground water. Cr[III] may be removed fromsolution as an amorphous precipitate (Cr(OH)₃) or as a solid solutionwith other metal oxides and hydroxides (Fe(OH)₃) (Palmer et al., 1994,Natural Attenuation of Chromium in Groundwater and Soils, EPA GroundWater Issue, EPA/540/5-94/505). Studies on reductive immobilization ofheavy metals and radionuclides are primarily laboratory scale.

The patent of Suthersan (U.S. Pat. No. 5,554,290) utilizes an in situanaerobic reactive zone for in situ precipitation and filtering out ofdissolved heavy metals as metallic sulfides, and microbialdenitrification to degrade nitrate to nitrogen gas. Although dithionitehas also been injected into wells to react with contaminants andprecipitate in place, use of dithionite is less attractive due to itstoxicity and cost.

Examples of bioremediation using soluble substrates include theaccelerated anaerobic pilot test (AAPT) conducted by the RemediationTechnologies Development Forum (RTDF), the hydrogen releasing compound(HRC®) and work with molasses. The AAPT evaluated the effectiveness ofinjecting lactate dissolved in water into the aquifer for establishingthe reducing conditions necessary for the reductive dechlorination ofTCE and cis-DCE to ethene. The treatment was performed using aclosed-loop approach, which included three up-gradient injection wellsand three down-gradient recovery wells. Recovered groundwater wasamended with lactate and re-injected into the up-gradient wells, thusclosing the loop. Lactate is a soluble readily biodegradable substrate.The results of this study were that lactate could effectively promoteanaerobic dehalogenation of the chlorinated solvents to non-toxic endproducts, but lactate addition resulted in biofouling of subsurfaceequipment.

HRC® is a commercially available lactate-based polymer material with aglycerol coating formulated and sold by Regenesis, Inc. (San Clemente,Calif.). It is reported to offer long-term availability of lactate(electron donor) to the aquifer via a time-release mechanism. In thesubsurface, HRC® slowly hydrolyzes, releasing dissolved lactate thattravels out into the aquifer enhancing reductive dehalogenation.

Molasses has been used for bioremediation studies because of its readyavailability, inexpensive cost, and rapid biodegradability. Whenmolasses was introduced into the aquifer as an electron donor via aninfiltration gallery that was dug to a depth immediately above theshallow groundwater table at a site in Lumberton, N.C., some biofoulingwas evidenced within one month of startup.

An early description of the use of insoluble oils in reductivedehalogenation is by Dybas et al. (1997, In Situ and On SiteBioremediation 3.59, Papers from the 4th Int. In Situ and On SiteBioremediation Symp., New Orleans, La.). Examples of bioremediationusing insoluble substrates include work with soybean oil by ParsonsEngineering Science (PES) (Denver, Colo.) and at an industrial site inHamilton, N.C. Work by PES at Defense Depot Hill Utah, DDHU and at theDepartment of Energy Facility (DOE, Pinnellas, Fla.) employs the directinjection of soybean oil in a field demonstration. In each study, oneinjection well was injected with excess soybean oil. The effects of theintroduction of oil were monitored in a set of down-gradient monitorwells. Results in the two studies indicate the initial absorption of thechlorinated solvents into the oil, followed by slow dissolution of thesolvents back into the groundwater and their subsequent reductivedechlorination. At the Hamilton, N.C. site a full-scale oil injectionwas performed by Solutions Industrial & Environmental Services, Inc.(Raleigh, N.C.), with approximately 200 inject points that were locatedthroughout the chlorinated solvent plume. Each injection point wasinjected with liquid soybean oil and the temporary injection well wasremoved.

The patent of Frederickson et al. (U.S. Pat. No. 5,265,674) disclosedtreatment of aquifers using an oil, such as vegetable oil or mineraloil, which is chosen to be less dense than water, so that the oil risesthrough the water and contaminant plume. In this method, reliance isplaced on partitioning of the contaminant in, and rising with, therising oil. In this work, mineral oil was preferred because of itsslower biodegradation rate.

It is an object of the invention to provide a safe, low-cost effectivemethod of bioremediation of aquifers using emulsified oil in the form ofan oil microemulsion. The method of the invention enhances a widevariety of anaerobic biodegradation processes in the subsurface byproviding a biodegradable, immobile organic substrate. Emulsifiedfood-grade insoluble oil is an inexpensive electron donor source. In theaquifer, the emulsion of the invention can provide for a naturallycoupled metabolic reaction between oil-degrading microorganisms anddehalorespiring microorganisms. Using emulsified oil according to theinvention allows for improved distribution of the oil laterally awayfrom the injection points and entrainment of the oil micro-droplets intothe effective pore space of the aquifer material. In addition, themethod of the invention may be implemented in a variety ofconfigurations, including PRB and broad area coverage.

Use of emulsified oil for in situ degradation of halogenated organiccompounds and perchlorate and for reductive immobilization of othercontaminants is a one-time activity. The naturally slow rate ofsubstrate dissolution and biodegradation establishes a naturallyoccurring time-release mechanism so that only the amount of substrate isused that will result in the desired biodegradation. Little substrate is“wasted” by non-specific biodegradation processes. The improved methodof distribution allows the process to be implemented in a variety ofconfigurations including PRB and broad area coverage. The use ofvertical injection wells offers the advantage of being able to place theoil emulsion in desired strata, or throughout the entire depth asdesired.

Other objects and advantages will be more fully apparent from thefollowing disclosure and appended claims.

SUMMARY OF THE INVENTION

The invention herein is a method for remediating aquifers andgroundwater contaminated, for example, by toxic halogenated organiccompounds, certain halogenated inorganic compounds, and oxidized heavymetals and radionuclides, using the introduction of an innocuous oil,preferably an edible, food-grade oil, preferably formulated into amicroemulsion by mixing with one or more natural food-grade emulsifiers(such as lecithin) and water. The invention provides a specific,time-release method of bioremediation. Pretreatment of the aquiferincreases mobility of the emulsion through the aquifer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the emulsified oil barrier configuration in Example 2.Substrate injection points are one inch diameter allowed PVC wells thatare screened from 10 to 43 feet below grade. Monitoring wells arelocated up-gradient and down-gradient of the barrier to evaluate theeffects of the emulsified oil barrier on contaminant concentrations.

In the Figure, a circled “X” shows a monitor well, a solid circle showsa substrate injection point, and a half-solid circle shows a gasmonitoring point. An identifying code is associated with each well andpoint.

FIG. 2 shows the monitoring results for sulfate (squares) and totalorganic carbon (triangles) from the monitor well identified as AA-113located directly down-gradient of the barrier in Example 2, as afunction of days since emulsion injection.

FIG. 3 shows the contaminant concentration data from monitor well AA-113located directly down-gradient of the barrier in Example 2, as afunction of days since emulsion injection. The concentration is shown ofthe following compounds: vinyl chloride (diamonds), 1,1-dichloroethene(solid triangles); 1,1-dichloroethane (X), cis-1,2-dichloroethene (solidsquares); 1,1,1-trichloroethane (solid circles); trichloroethene (hollowtriangles); and tetrachloroethene (hollow circles).

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF

The present invention provides a method for remediating aquiferscontaminated by a variety of different contaminants. The method of theinvention typically comprises, a site evaluation, pretreatment,treatment and post-treatment as discussed herein and in the examples.

There are three main types of bioremediation processes that may beaccomplished with the invention herein: 1) dehalogenation of halogenatedorganic compounds; 2) anaerobic biodegradation of inorganic contaminantsincluding reduction of nitrates, sulfates, and perchlorates; and 3)anaerobic immobilization of soluble compounds to form insolublecompounds. In the first instance, the invention herein is a process bywhich the anaerobic reductive dehalogenation of toxic halogenatedorganic compounds is promoted by the addition of a food-grade, slowlysoluble, emulsified oil substrate into the aquifer. In the invention,the biodegradable, slowly soluble oil provides both carbon substrate andelectron donor to stimulate the growth of natural and/or introducedpopulations of microorganisms. This metabolism results in creation ofanaerobic subsurface conditions that promote the activity of secondaryindigenous or amended populations of anaerobic dehalogenating bacteria.The metabolic process is known as reductive dehalogenation. Theorganisms degrade the toxic organic compounds contained in thegroundwater as the groundwater moves through the aquifer. The result ofthe process is the biological transformation of the toxic halogenatedorganic compounds into non-toxic non-halogenated end products.

Chlorinated aliphatic compounds that may be biologically transformed bythis process include tetrachloroethene (PCE), trichloroethene (TCE), cis& trans-dichloroethene (DCE), vinyl chloride (VC), 1,1,1-trichloroethane(TCA), 1,1- and 1,2-dichloroethane (DCA), chloroethane (CA), carbontetrachloride (CTC), chloroform (CF), methylene chloride (DCM) andrelated solvents and degradation products containing halogens includingchlorine, fluorine, bromine and iodine. Chlorinated aromatic compoundsthat may be biologically transformed by this process include chlorinatedbenzenes, chlorinated phenols, chlorinated biphenyls and relatedcompounds and degradation products. The result of the process is theformation of non-toxic metabolic end products or metabolic products thatmay be more easily degraded through aerobic biological processes orphysical-chemical processes.

An example of the anaerobic processes utilized with the invention is themicrobially mediated degradation of perchlorate (ClO₄ ⁻), chlorate (ClO₃⁻), and chlorite (ClO₂ ⁻) in groundwater, which is promoted by theaddition of a food-grade, slowly soluble, emulsified oil substrate intothe aquifer. The result of the process is the reduction of thecontaminants yielding chloride (Cl⁻) and oxygen.

The invention enables the immobilizing of oxidized metals andradionuclides by promoting anaerobic, reducing conditions through theaddition of a food-grade, slowly soluble, emulsified oil substrate intothe aquifer. Compounds that may be immobilized through this processinclude chromium (Cr), uranium (U) and technetium (Tc), as well as othermaterials that may be immobilized by converting them from a moreoxidized condition to a more reduced condition.

In particular, the preferred method of the invention comprises the stepsof 1) evaluation of a selected site that is to be bioremediated; 2)pretreatment of the site to increase mobility of treatment materialsthrough the site; 3) treatment of the site; 4) post-treatment of thesite; and 5) monitoring and evaluation of the site after treatment.

Site Evaluation. Site evaluation includes determination of the type andamount of undesirable contaminant in the area of the aquifer, such ashalogenated aliphatic or aromatic organic compounds which arehalorespired by the microorganisms (e.g., compounds containing chlorine,bromine, iodine or fluorine); inorganic compounds that may be degradedthrough anaerobic processes (e.g., compounds containing nitrate; sulfateor perchlorate); and soluble compounds that may be anaerobicallyimmobilized to an insoluble form (e.g., compounds containing chromium,uranium, or technetium). Anaerobic immobilization using the inventionmay be increased in some instances by the addition of sulfate, to yielda sulfide precipitate according to the patent of Suthersan (discussedabove). For each of these types of contaminants, the bacteriaenzymatically use an edible oil as an electron donor with thecontaminant, such as a chlorinated solvent as the electron acceptor, torelease energy.

Additional site evaluation may include obtaining samples of thegroundwater and soil from the aquifer, to which one or more oils areadded, followed by measurement of, the loss of contaminant and thebiodegradation of the oil with time (e.g., 6 months). Similarly,different forms of the same oil (e.g., liquid or semi-solid) may betested in parallel samples from the aquifer. With increased experiencewith a particular type of aquifer, qualitative judgments may allow areduction in the amount of preliminary evaluation that is necessary.

Site evaluation may also include preliminary placement of a small numberof treatment points at the actual site, such as 3-4 points in a row orbarrier, followed by some portion or all of the actual pretreatment,treatment and post-treatment at the limited site, with follow-upanalysis for six months or so to see if groundwater down-gradient of thebarrier has been remediated.

Pretreatment. The process of the invention preferably includes thepretreatment of certain portions of the aquifer with chemical agents toreduce the sorption, and/or entrapment of the oil-emulsifier droplets bythe aquifer material. Typically the pretreatment agent is an emulsifier,for example, lecithin, as might be later used in the treatment step, ora calcium, sodium or phosphate salt which are added in order to fill orsaturate the soil surfaces so that the later oil-emulsion treatmentflows better through the aquifer. The selected chemical pretreatmentagent(s) may be injected first to improve distribution of the oil inaquifer followed by the oil emulsion, and then water or additionaltreatment solution to distribute the oil. Pretreating a portion of theaquifer as discussed herein allows the identification of the zone withinthe aquifer into which the oil emulsion is injected and a means forinjecting the emulsion, with or without pressure, to optimize thedistribution of the oil emulsion away from the injection points. In atypical pretreatment of the invention, the emulsifier is introduced intothe aquifer via vertically installed temporary or permanent wells. Inthis manner, oil elusion may later be injected to blanket the entiresaturated thickness of the aquifer, or to reside in a given stratum.

The pretreatment volume of the substances added to the aquifer and theemulsifier concentration are preferably selected based on computermodeling of the injection process. The primary parameters controllingthis are: (1) injection well spacing; (2) vertical variation in aquiferpermeability; (3) aquifer dispersivity; (4) adsorption isotherm ofemulsifier to the aquifer matrix; and (5) oil-in-water emulsion volume.Vertical variations in aquifer permeability are estimated based onlithologic descriptions of the aquifer material. The dispersioncoefficient can be estimated from previously published reports ofaquifer dispersivity (see Bedient et al., 1999, Ground WaterContamination—Transport and Remediation, 2nd Ed., Prentice Hall, UpperSaddle River, N.J.; Domenico et al., 1998. Physical and ChemicalHydrogeology, 2nd Ed., John Wiley & Sons, New York. The adsorptionisotherm of emulsifier to the aquifer matrix can be estimated by mixinga emulsifier solution of known concentration with aquifer solids,allowing the solution to equilibrate and measuring the new emulsifierconcentration in solution. Replicate samples at several differentemulsifier concentrations are preferably run to develop reliableinformation: The above-cited references also provide more detaileddescriptions of the procedure as known in the art for measuring theadsorption isotherm.

Other materials may be added to the pretreatment solutions to reduce theadsorption of the emulsifying agent and/or enhance the mobility of theoil-in-water emulsion including cations (Ca⁺⁺, Na⁺, NH₄ ⁺), anions (Cl⁻,PO₄ ⁻) and other chemical agents (lecithin, polyphosphate and otheravailable food-grade materials).

When pretreatment comprises use of emulsified oils, the considerationsand methodology are as discussed below for the treatment phase.

Treatment. The invention utilizes the introduction of one or moreedible, food-grade innocuous oils formulated into a microemulsion bymixing with one or more natural food-grade emulsifiers and water.

The oil used in the invention is preferably a food-grade liquid soybeanoil. It is anticipated that liquid soybean oil is a satisfactory oil foruse in the, invention for most aquifers to be remediated; however,semi-solid or solid soybean oil, or other oils may be found to bepreferable in particular types of aquifer. Such factors as biologicalactivity of the groundwater, methane production, and the results of labmicrocosm studies will enable optimizing use of the invention inparticular aquifers. Other oils usable in the invention include cornoil, canola oil, olive oil, peanut oil, coconut oil, palm oil, rape oil,fish oil, butter, and animal tallow. If there are not regulatoryrestrictions, non-food oils including castor oil, cottonseed oil,linseed oil, tung oil, and other mineral oils, waxes and paraffins maybe used. The oils used in the invention may be modified by hydrogenationto reduce their aqueous solubility and increase their melting point, andthus may also be viscous, semi-solid, or solid. Use of alternative oilsmay be useful in cases where the rate of oil biodegradation is toorapid, thus excessively decreasing the operating life of the barrier.Considerations affecting selection of the oil for bioremediation at aparticular site include the desirability of having an oil that: (1) islow cost; (2) is a food-grade, Generally Recognized As Safe (GRAS),non-toxic oil; (3) has low solubility so the oil is not dissolved awaytoo quickly; (4) is sufficiently resistant to non-biological andbiological degradation to persist for several years in an aquifer; (5)is sufficiently biodegradable to support the biologicaldegradation/immobilization of the problem contaminants, and (6) is easyto handle.

The oil to be used at a particular site may be selected based onbiodegradability so that it does not degrade too slowly or too rapidly.Higher molecular weight, less-soluble oils may thus be used where slowerbiodegradation is preferred.

The total oil volume to be used at a site is selected to providesufficient oil to enhance the biodegradation of the contaminants andcompeting electron acceptors (oxygen, nitrate, sulfate, iron) that enterthe barrier with some extra material remaining to allow for slow releaseof dissolved substrate to the groundwater. This volume is determinedbased on the groundwater velocity, concentration of contaminants andcompeting electron acceptors entering the barrier, concentration ofsubstrate to be released from the barrier, known ratios of substrate(oil) to other compounds required for biodegradation and the proposeddesign life of the barrier. Preferably, at a particular site, sufficientoil is added to last for a specific amount of time, for example, five orten years. Concentrations of contaminants and competing electronacceptors are estimated from groundwater monitoring data.

The emulsifier used in the invention is preferably non-toxic, is capableof forming stable oil-in-water emulsions under the environmentalconditions present at the aquifer site, and is characterized in that itssorption and/or attachment to the aquifer material can be controlled inthe environment to move through the aquifer at the desired rate. Liquidlecithin, typically used as an emulsifier in the food industry, is thepreferred emulsifier and stabilizer for the oil in the invention herein.The advantages of using lecithin are that it is an accepted food-gradematerial known to meet regulatory requirements. Other potentialemulsifiers and stabilizers include milk solids, carrageenan, guar gum,locust bean gum, karaya gum, zanthan gum, pectin, polysorbate,phosphates, and related compounds. If there are no regulatoryrestrictions, non-food emulsifiers may be used. Considerations forselecting the emulsifier are that it should: (1) be low cost; (2) be afood-grade, Generally Recognized As Safe (GRAS), and non-toxicemulsifier; (3) have an appropriate hydrophobic-lipophilic balance (HLB)for the oil being used; (4) produce a stabile emulsion with an averagedroplet size less than the mean pore size of the sediment; (5) notexcessively adsorb into the aquifer sediment; (6) be more biodegradablethan the oil being mobilized; and (7) be easy to handle. Selection ofthe correct mixer and mixing regimen also helps to ensure that thedroplet size of the emulsion is correct so that the droplets of theemulsion can move through the pores between the sand grains. When theoil used in the invention is solid or semi-solid, the appropriate stepsas known in the art to form an emulsion (e.g., emulsifying in hot wateror providing small particles of the solid oil prior to forming theemulsion) are used to obtain the proper emulsion droplet size andcharacteristics.

The lecithin to oil ratio is preferably about 1:5 (range of about 1:3 toabout 1:10 for typical aquifers. This ratio is selected to: (1) providea sufficiently high lecithin concentration to stabilize the oil-in-wateremulsion; (2) provide an excess of lecithin to allow for some additionaladsorption of lecithin to the aquifer matrix, and (3) have suitablehandling properties for work in the field (acceptable viscosity somaterial can be pumped and mixed with typical field equipment at theambient field temperature).

The ratio of water to oil-lecithin mixture in the injection emulsion isselected: (1) to ensure that water is the continuous phase in theemulsion (by forming an oil-in-water emulsion, this allows the emulsionto be easily mixed with water); (2) so that the injection emulsion hasan acceptable viscosity which allows easy injection, and (3) to enabledistribution of the oil over a sufficiently large volume of aquifer toprevent excessive permeability loss (oil and emulsifier are alwayspreblended to get better mixing before mixing with water). Because ofthe large proportion of water in the treatment fluids, the fluid flowswith the water in the aquifer rather than flowing upward. Typically aminimum of 3-5 volumes of water to 1 volume of oil-lecithin mixture isused to achieve an oil-in-water emulsion. Using this ratio also resultsin a viscosity less than 2 centipoise, which is usually acceptable. Toachieve the selected ratio of water and oil-lecithin, appropriateadjustments are made of the flow rate of the oil-lecithin mixture andthe flow rate of the water into the high-speed mixer to be used to formthe emulsion. The oil should also be distributed over a sufficientvolume of aquifer to prevent excessive clogging of the aquifer porespaces. The oil saturation should be a maximum of 12% of the aquiferpore spaces to prevent excessive permeability loss, however, lowersaturations (1 to 5%) are desirable.

In the invention, the process of emulsifying the oil with aid of a shearmixing apparatus and injecting it under pressure assures that a stableemulsion containing micro-droplets of uniform size, such that the meandroplet size is less than the mean pore size of the aquifer to betreated at the required flow-rate and pressure for this application, canbe entrained into the effective pore space in the aquifer material. Thisassures a greater longevity in the subsurface and reduces the likelihoodthat the oil will coalesce and float to the surface of the aquifer. In atypical fine sand, for example, the average pore size is approximately1.0 micron, so the average droplet preferably has a diameter less than1.0 micron.

Food-grade emulsified oil can be introduced into the contaminatedaquifer in either of two configurations: 1) forming a permeable reactivebarrier (PRB) perpendicular to the flow and transport of dissolvedgroundwater contamination, and 2) distributing the emulsified oil acrossthe areal extent of the plume or source area to effect an immediateremediation throughout the aquifer.

In the invention, the one or more selected oils are introduced into thecontaminated area via a series of injection points. The injection pointsmay be installed to form a permeable reactive barrier (PRB) arranged tointercept the down-gradient movement of the contaminant(s) in thegroundwater contaminant plume, to provide broad coverage of the impactedarea, or to address the source area of contamination. Injection can beperformed through small diameter boreholes or injection wells (temporaryor permanent) emplaced into the aquifer via direct push technology suchas Geoprobe® manufactured by Geoprobe Systems, Salina, Kans.) orequivalent apparatus, or via temporary or permanent injection wellsinstalled via standard drilling methods. The decision regarding thedepth of the drilling is determined, as is known in the art, frominformation about the vertical profile of the contamination in theaquifer. While it is desirable to screen the entire saturated thicknessof the aquifer, from the soil-groundwater interface to the bottom of theaquifer, such depths may not be practical or necessary. Target depthsshould offer the best chance for the contaminated groundwater to come incontact with the emulsified oil.

Emplacement of the oil emulsion is preferably performed in one ofseveral ways. The oil emulsion may be injected through the screened endof the direct push point as it is withdrawn, essentially grouting thehole with oil. Alternatively, a temporary well may be installed in aborehole. Then, the riser of one or more boreholes may be affixed with avalve to which the oil emulsion delivery apparatus can be attached. Allfluids are typically injected under pressure. After pumping, thedelivery hose is detached and the temporary well casing either extractedfrom the hole or buried in place as is known in the art. The inventionherein provides a process that can address the entire groundwater plumein situ.

By using vertical injection points, the oil can be placed throughout theplume, effectively addressing all portions of the plume simultaneously.

During the injection process, injection flow rates are adjusted toensure that there is at least 10 psi of pressure buildup in eachinjection well. This pressure buildup is required to achieve reasonablyuniform emulsified oil distribution over the vertical interval of theinvention well. Maximum injection pressures should also be controlled toprevent blowout of the well. In certain cases, it may be desirable touse very high injection pressures to enhance hydraulic fracturing of theformation and enhances oil spread. However, this is a special case andneeds to be closely controlled.

Also, during pretreatment or treatment, if the environmental conditionsin the immediate vicinity of the barrier are not optimum for the desiredrate of biodegradation to occur, other chemical agents as are known inthe art may be added to the injection stream (oil or water) to changethe conditions in the subsurface to make them closer to optimum.

Post-treatment. Following injection of the oil-in-water emulsion, apost-treatment pulse of emulsifier, such as lecithin, in water solutionis fed into the wells to reduce mixing of the oil-in-water emulsion withplain water and to displace more of the oil away from the injectionwell. Typically, post-treatment comprises the addition of emulsifier,followed by addition of water to the aquifer. The post-treatmentemulsifier (e.g., lecithin) concentration is selected to match the ratioof lecithin to water in the oil-in-water emulsion. The post-treatmentvolume is selected based on computer modeling of the injection processto minimize mixing of the emulsion with plain water. The primaryparameters controlling this are: (1) injection well spacing; (2)vertical variation in aquifer permeability; (3) aquifer dispersivity;(4) adsorption isotherm of lecithin to the aquifer matrix; and (5)oil-in-water emulsion volume.

Monitoring and Evaluation. To determine that a barrier is performing asdesired, evidence of good performance is obtained. Such evidencetypically includes data indicating that: (1) the contaminants aredegraded to required levels; (2) there is little bypassing ofcontaminants around barrier; (3) the permeability changes in the aquifersurrounding the injection wells are within acceptable ranges; and (4)there are acceptable rates of substrate depletion in the barrier.Substrate depletion rates can be estimated based on the concentrationsof contaminants, competing electron acceptors, and electron donorsentering and being released from the barrier. If monitoring results aredifferent than those used in the original design calculations, then thedesign may be modified prior to fill-scale implementation.

After injection of the oil emulsion has been completed, the “invention”works without further operation and maintenance. The oil emulsion slowlydissolves as a time-release electron donor, thus stimulating indigenousmicrobial activity in the subsurface.

The features of the present invention will be more clearly understood byreference to the following examples, which are not to be construed aslimiting the invention.

EXAMPLES Example 1 Preliminary Studies

Preliminary biodegradability screening studies were first conducted toevaluate edible oils (liquid soybean oil and semi-solid soybean oil, ascompared to molasses) for their potential use in a biologically activebarrier system. Laboratory microcosm experiments showed that reductivedehalogenation was most rapid in the microcosm amended with semi-solidsoybean oil. TCE and DCE were reduced to below detection within twomonths with concurrent production of vinyl chloride and ethene. After130 days of incubation, vinyl chloride in the headspace was reduced tonear the analytical detection limit with essentially complete conversionof TCE to ethene. Molasses and liquid soybean oil also stimulatedreductive dehalogenation; however ethene production was slower than forthe semi-solid soybean oil.

Example 2 Pilot Test

An extensive pilot test of this process is being conducted in achlorinated solvent plume at Dover Air Force Base near Dover, Del. Theprimary contaminants at this site include tetrachloroethene (PCE),trichloroethene (TCE) and dichloroethene (DCE). Two different barrierconfigurations are being evaluated: 1) injection of liquid soybean oilin closely spaced wells; and 2) injection of a soybean and lecithinoil-in-water emulsion in moderately spaced wells (see FIG. 1). Eachbarrier is constructed with 1-inch diameter continuously screened directpush wells.

In Barrier 1, about 20 gallons of liquid soybean oil were injected intoeach well followed by about 100 gallons of groundwater resulting in 18to 24 inch cylindrical plugs of oil spaced 24-inches on center (OC).

In Barrier 2, a soybean oil-in-water emulsion was injected into wellsspaced 5 ft. OC followed by 1,000 gallons of groundwater to distributethe oil resulting in 6 to 8 ft.-diameter cylindrical columns of treatedsediment spaced 5 ft. OC. Prior to beginning the injection, alecithin-oil mixture was prepared having a ratio of 10 gallons oil to 1gallon lecithin. The oil-in-water emulsion was then prepared by passinga mixture of eight gallons of water per gallon of the lecithin-oilmixture through a high shear mixer to generate a microemulsion havingless than 1 micron diameter droplets. Injection of 1000 gallons of theoil-in-water emulsion was followed by injection of 1000 gallons of waterper well. Each well had a screen opening from 10 to 42 ft below groundsurface (BGS). Monitor wells located up-gradient and down-gradient ofeach barrier enables evaluation of the effectiveness of each approachfor distributing the oil and enhancing chlorinated adventbiodegradation.

FIG. 2 shows the monitoring results from a monitor well located directlydown-gradient of the barrier. Dissolved organic carbon increaseddramatically down-gradient of the barrier and the competing electronacceptor sulfate declined to below the detection limit, indicating verygood conditions are being achieved for anaerobic biodegradation of thechlorinated solvents. FIG. 3 shows the contaminant concentration datafor the same well. The concentration of all of the higher chlorinatedcompounds, PCE, TCE and DCE, has declined, indicating anaerobicbiodegradation is occurring. Vinyl chloride (VC) is produced as anintermediate product in this process. VC increases from below detectionconcentration to 51 μg/L, indicating anaerobic degradation of the othercompounds is occurring. It is expected that VC will begin to decreasesoon with a concurrent production of the non-toxic endproduct ethene.

Example 3 Site Remediate Process

Planning for Treatment. A food-grade edible oil is distributed at twolocations at the subsurface at Edwards Air Force Base, Calif. to treatsoil and groundwater contaminants utilizing the invention. At the firstlocation, the primary contaminant is trichloroethylene (TCE). At thesecond site, the primary contaminant is perchlorate (ClO₄ ⁻). Theinjection procedure is similar at the two sites. At the TCE site, thegroundwater table occurs at 45 to 50 ft. below ground surface and flowsdown-gradient at an average groundwater velocity of 40 feet per year.The objective of this process is to construct a barrier to contaminantmigration by installing a series of wells in a row generallyperpendicular to the groundwater flow direction. A low solubility edibleoil microemulsion is injected into the wells and distributed throughoutthe surrounding aquifer. Sufficient oil is distributed throughout theaquifer to enhance the biotransformation of TCE entering the barrier tothe innocuous degradation product ethene through a process calledreductive dehalogenation for ten years. Prior to the start of theinjection project, a site characterization was completed to generallydefine the horizontal and vertical distribution of the contaminant plumeand the chemistry of the groundwater in the vicinity of the proposedinjection. In general, the groundwater has a neutral to slightlyalkaline pH (7 to 8), moderate dissolved oxygen (1-4 mg/L), and highsulfate concentration (100-1000 mg/L). Sufficient emulsified oil must bedistributed through the aquifer to enhance the biodegradation of thecontaminants and competing electron acceptors (oxygen, nitrate, sulfate,iron) with some extra material remaining to allow for slow release ofdissolved substrate to the groundwater. The actual treatment protocol isas follows.

Materials. The food-grade edible oil used is liquid soybean oil(Centrapour Salad Oil from Central Soya, Fort Wayne, Ind.). Liquidlecithin (Centrolene A from Central Soya, Fort Wayne, Ind.) is used asthe emulsifier and stabilizer for the oil.

Pilot Study. As the first step in developing a barrier at this site, asix-month long pilot test is conducted. In the pilot test, fourinjection wells are installed 7.5 ft. apart in a line generallyperpendicular to the groundwater flow direction. An oil-in-wateremulsion is injected into each of these wells to distribute andimmobilize a biodegradable, edible oil in a roughly 9.3 ft diametercolumn of aquifer surrounding each well. The 9.3 ft diameter is selectedto provide a reasonable overlap from one injection well to the next.Monitoring wells are installed up-gradient and down-gradient of thebarrier and are monitored periodically for the contaminants, degradationproducts, competing electron acceptors (oxygen, nitrate, sulfate,methane) and indicator parameters to judge the success of the project.Based on the success of the pilot study, additional wells are installedand injected to extend the barrier across the full width of thecontaminant plume.

Following installation of the pilot scale barrier, a monitoring programutilizing standard techniques is conducted to ensure that the pilotscale barrier is performing as desired.

Injection Wells. Injection wells are installed with a screened intervalfrom 45 to 65 ft below ground surface (BGS). At this location, most ofthe contamination is present in the region from 45 to 55 ft BGS. Becauseinjection of the oil typically results in roughly a factor of tenreduction in aquifer permeability which could cause bypassing of thecontaminants around the treatment zone, the potential impacts ofcontaminant bypassing are evaluated. The evaluation may be done using aseries of computer models (publicly available models MODFLOW and MT3Davailable from the U.S. Geological Survey, Reston, Va. and the U.S.Environmental Protection Agency, Center for Subsurface Modeling Support,Ada, Okla. to simulate groundwater flow and solute transport in thevicinity of the proposed barrier. Results of these simulation indicatedthat the barrier would need to extend from 45 to 65 ft BGS to preventbypassing of the contaminants. The injection equipment, tanks, mixersand associated equipment are assembled near the injection site andtested to ensure the system is operating properly.

Pretreatment. The aquifer surrounding each well is first pretreated witha lecithin-in-water solution to reduce entrapment of the subsequentoil-in-water emulsion. Liquid lecithin is fed into the high shear mixerat a ratio of 1 gallon lecithin per 17 gallon water until 630 gallons ofwater and 37 gallons of lecithin have been injected into each well usinga predetermined pretreatment volume and lecithin concentration.

Treatment. After pretreatment, the aquifer surrounding each well istreated with the oil-in-water emulsion. Liquid lecithin is first blendedwith liquid soybean oil at a ratio of 1 gallon lecithin to 4.5 gallonoil. The lecithin-oil mixture is then fed into the water supply enteringthe high shear mixer at a ratio of 1 gallon lecithin-oil mixture per 5gallons water until 1000 gallons of water and 200 gallons oflecithin-oil mixture have been injected into each well.

Post-treatment. To accomplish a reduction in mixing of the oil-in-wateremulsion with plain water and to displace more of the oil away from theinjection well, liquid lecithin is fed into the high shear mixer at aratio of 1 gallon lecithin per 17 gallons water until 630 gallons ofwater and 37 gallons of lecithin have been injected into, each well.Finally, 2000 gallons of plain water are injected to displace theoil-in-water emulsion away from the injection well a sufficient distanceto, (1) prevent excessive permeability loss; and (2) treat the requiredvolume of aquifer.

While the invention has been described with reference to specificembodiments, it will be appreciated that numerous variations,modifications, and embodiments are possible, and accordingly, all suchvariations, modifications, and embodiments are to be regarded as beingwithin the spirit and scope of the invention.

1. A method for remediating a selected aquifer in a sediment having amean pore size to reduce contaminants in the aquifer, comprising: a)evaluating the aquifer for contaminant identity and location, b)determining whether aquifer pretreatment should be done, and if so,pretreating the aquifer, c) treating the aquifer with a selected amountof an oil microemulsion having an average droplet size less than themean pore size of the sediment, d) determining whether aquiferpost-treatment should be done, and if so, post-treating the aquifer; ande) monitoring the aquifer to determine if remediation has beenaccomplished.
 2. The method according to claim 1, wherein thecontaminants in the aquifer are selected from the group consisting ofhalogenated organic compounds, inorganic compounds that may be degradedthrough anaerobic processes, and soluble compounds that may beimmobilized to form insoluble compounds.
 3. The method according toclaim 1, wherein the oil microemulsion comprises a food-grade, slowlysoluble, emulsified oil substrate.
 4. The method according to claim 1,wherein the pretreatment comprises pretreatment of certain portions ofthe aquifer with a chemical agent selected from the group consisting ofagents that reduce sorption of the oil microemulsion by the aquifermaterial, and agents that reduce entrapment of the oil microemulsion bythe aquifer material.
 5. The method according to claim 4, wherein thechemical agent is an emulsifier.
 6. The method according to claim 5,wherein the emulsifier is lecithin.
 7. The method according to claim 4,wherein the chemical agent is a salt selected from the group consistingof calcium, sodium and phosphate salts.
 8. The method according to claim4, wherein the pretreatment further comprises injecting an oilmicroemulsion, and then water, after pretreatment with the chemicalagent.
 9. The method according to claim 1, wherein the oil microemulsioncomprises an oil selected from the group consisting of soybean oil, cornoil, canola oil, olive oil, peanut oil, coconut oil, palm oil, rape oil,fish oil, butter, and animal tallow.
 10. The method according to claim9, wherein the oil is a food-grade liquid soybean oil.
 11. The methodaccording to claim 9, wherein the oil has been modified by hydrogenationto reduce aqueous solubility and increase melting point.
 12. The methodaccording to claim 1, wherein the selected amount of the oilmicroemulsion is determined using groundwater velocity, concentration ofcontaminants and competing electron acceptors, known ratios of oil toother compounds required for biodegradation, a preferred concentrationof the oil microemulsion, and a length of time for the treatment tolast.
 13. The method according to claim 1, wherein the oil microemulsionis formed using an emulsifier.
 14. The method according to claim 13,wherein the emulsifier is non-toxic, is capable of forming stableoil-in-water microemulsions under the environmental conditions presentat the aquifer site, and is characterized in that its sorption andattachment to the sediment in the aquifer can be controlled to movethrough the aquifer at a desired rate.
 15. The method according to claim13, wherein the emulsifier is selected from the group consisting oflecithin, milk solids, carrageenan, guar gum, locust bean gum, karayagum, zanthan gum, pectin, polysorbate, and phosphates.
 16. The methodaccording to claim 15, wherein the emulsifier is lecithin.
 17. Themethod according to claim 13, wherein the ratio of emulsifier to oil inthe oil microemulsion is about 1:3 to 1:10.
 18. The method according toclaim 1, wherein the oil microemulsion is mixed with water.
 19. Themethod according to claim 18, wherein the ratio of oil microemulsion towater is about 1:3 to 1:10.
 20. The method according to claim 1, whereinthe aquifer is treated using a permeable reactive barrier perpendicularto flow and transport of dissolved groundwater contamination in theaquifer.
 21. The method according to claim 20 wherein the monitoringcomprises collecting data indicating that: (1) the contaminants aredegraded to required levels; (2) there is little bypassing ofcontaminants around the barrier; (3) the permeability changes in theaquifer surrounding the injection wells are within acceptable ranges;and (4) there are acceptable rates of substrate depletion in thebarrier.
 22. The method according to claim 1, wherein the contaminant isfrom a source area and is in a plume having an areal extent, and theaquifer is treated by distributing the oil microemulsion across theareal extent of the plume or source area to effect an immediateremediation throughout the aquifer.
 23. The method according to claim 1,wherein the aquifer is treated by injecting the oil microemulsionthrough an end of a direct push point as the push point is withdrawn,forming a borehole, using injection flow rates adjusted to ensure thatthere is at least 10 psi of pressure buildup in the borehole.
 24. Themethod according to claim 1, wherein the aquifer is treated by injectingthe oil microemulsion using a temporary well installed in a borehole.25. The method according to claim 1, wherein the aquifer is treated withthe oil microemulsion in injection wells using injection flow ratesadjusted to ensure that there is at least 10 psi of pressure buildup ineach injection well.
 26. The method according to claim 1, whereinpost-treatment of the aquifer comprises a post-treatment pulse ofemulsifier.
 27. The method according to claim 26, further comprisingaddition of water to the aquifer.
 28. A method for remediating aselected aquifer in a sediment having a mean pore size to reducecontaminants in the aquifer, comprising: a) evaluating the aquifer forcontaminant identity and location, b) determining whether aquiferpretreatment should be done, and if so, pretreating the aquifer, whereinthe pretreatment comprises pretreatment of certain portions of theaquifer with a chemical agent which is an emulsifier selected from thegroup consisting of lecithin, milk solids, carrageenan, guar gum, locustbean gum, karaya gum, zanthan gum, pectin, polysorbate, and phosphates,c) treating the aquifer with a selected amount of an oil microemulsionhaving an average droplet size less than the mean pore size of thesediment, d) determining whether aquifer post-treatment should be done,and if so, post-treating the aquifer, and e) monitoring the aquifer todetermine if remediation has been accomplished.
 29. A method forremediating a selected aquifer in a sediment having a mean pore size toreduce contaminants in the aquifer, comprising: a) evaluating theaquifer for contaminant identity and location, b) treating the aquiferwith a selected amount of an oil microemulsion having an average dropletsize less than the mean pore size of the sediment, wherein the oilmicroemulsion comprises a food-grade liquid soybean oil, c) determiningwhether aquifer post-treatment should be done, and if so, post-treatingthe aquifer, and d) monitoring the aquifer to determine if remediationhas been accomplished.
 30. A method for remediating a selected aquiferin a sediment having a mean pore size to reduce contaminants in theaquifer, comprising: a) evaluating the aquifer for contaminant identityand location, b) determining whether aquifer pretreatment should bedone, and if so, pretreating the aquifer, c) treating the aquifer with aselected amount of an oil microemulsion having an average droplet sizeless than the mean pore size of the sediment, wherein the oilmicroemulsion comprises an oil selected from the group consisting ofsoybean oil, corn oil, canola oil, olive oil, peanut oil, coconut oil,palm oil, rape oil, fish oil, butter, and animal tallow, and wherein theoil has been modified by hydrogenation to reduce aqueous solubility andincrease melting point, d) determining whether aquifer post-treatmentshould be done, and if so, post-treating the aquifer, and e) monitoringthe aquifer to determine if remediation has been accomplished.
 31. Amethod for remediating a selected aquifer in a sediment having a meanpore size to reduce contaminants in the aquifer, comprising: a)evaluating the aquifer for contaminant identity and location, b)determining whether aquifer pretreatment should be done, and if so,pretreating the aquifer, c) treating the aquifer with a selected amountof an oil microemulsion having an average droplet size less than themean pore size of the sediment, wherein the oil microemulsion is formedusing an emulsifier, and wherein the emulsifier is selected from thegroup consisting of lecithin, milk solids, carrageenan, guar gum, locustbean gum, karaya gum, zanthan gum, pectin, polysorbate, and phosphates,d) determining whether aquifer post-treatment should be done, and if so,post-treating the aquifer, and e) monitoring the aquifer to determine ifremediation has been accomplished.
 32. A method for remediating aselected aquifer in a sediment having a mean pore size to reducecontaminants in the aquifer, comprising: a) evaluating the aquifer forcontaminant identity and location, b) determining whether aquiferpretreatment should be done, and if so, pretreating the aquifer, c)treating the aquifer with a selected amount of an oil microemulsionhaving an average droplet size less than the mean pore size of thesediment, wherein the oil microemulsion is formed using an emulsifier,and, wherein the emulsifier is lecithin, d) determining whether aquiferpost-treatment should be done, and if so, post-treating the aquifer, ande) monitoring the aquifer to determine if remediation has beenaccomplished.
 33. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,comprising treating the aquifer with a selected amount of an oilmicroemulsion having an average droplet size less than the mean poresize of the sediment, wherein the oil microemulsion comprises an oilselected from the group consisting of soybean oil, corn oil, canola oil,olive oil, peanut oil, coconut oil, palm oil, rape oil, fish oil, butterand animal tallow, and in which the oil microemulsion acts to stimulatethe growth of microorganisms.
 34. A method for remediating a selectedaquifer in a sediment having a mean pore size to reduce contaminants inthe aquifer, comprising treating the aquifer with a selected amount ofan oil microemulsion having an average droplet size less than the meanpore size of the sediment, wherein the oil is an edible liquid soybeanoil.
 35. A method for remediating a selected aquifer in a sedimenthaving a mean pore size to reduce contaminants in the aquifer,comprising treating the aquifer with a selected amount of an oilmicroemulsion having an average droplet size less than the mean poresize of the sediment, wherein the oil microemulsion is formed using anemulsifier, and wherein the emulsifier is selected from the groupconsisting of lecithin, milk solids, carrageenan, guar gum, locust beangum, karaya gum, zanthan gum, pectin, polysorbate, and phosphates.
 36. Amethod for remediating a selected aquifer in a sediment having a meanpore size to reduce contaminants in the aquifer, comprising treating theaquifer with a selected amount of an oil microemulsion having an averagedroplet size less than the mean pore size of the sediment, wherein theoil microemulsion is formed using an emulsifier and wherein theemulsifier is lecithin.
 37. A method for remediating a selected aquiferin a sediment having a mean pore size to reduce contaminants in theaquifer, comprising: a) evaluating the aquifer for contaminant identityand location, b) treating the aquifer with a selected amount of an oilmicroemulsion having an average droplet size less than the mean poresize of the sediment, wherein the oil microemulsion comprises an oilselected from the group consisting of soybean oil, corn oil, canola oil,olive oil, peanut oil, coconut oil, palm oil, rape oil, fish oil, butterand animal tallow, and in which the oil microemulsion acts to stimulatethe growth of microorganisms, and c) monitoring the aquifer to determineif remediation has been accomplished.
 38. A method for remediating aselected aquifer in a sediment having a mean pore size to reducecontaminants in the aquifer, comprising: a) evaluating the aquifer forcontaminant identity and location, b) treating the aquifer with aselected amount of an oil microemulsion having an average droplet sizeless than the mean pore size of the sediment, wherein the oil is anedible liquid soybean oil, and c) monitoring the aquifer to determine ifremediation has been accomplished.
 39. A method for remediating aselected aquifer in a sediment having a mean pore size to reducecontaminants in the aquifer, comprising: a) evaluating the aquifer forcontaminant identity and location, b) treating the aquifer with aselected amount of an oil microemulsion having an average droplet sizeless than the mean pore size of the sediment, wherein the oilmicroemulsion is formed using an emulsifier, and wherein the emulsifieris selected from the group consisting of lecithin, milk solids,carrageenan, guar gum, locust bean gum, karaya gum, zanthan gum, pectin,polysorbate, and phosphates, and c) monitoring the aquifer to determineif remediation has been accomplished.
 40. A method for remediating aselected aquifer in a sediment having a mean pore size to reducecontaminants in the aquifer, comprising: a) evaluating the aquifer forcontaminant identity and location, b) treating the aquifer with aselected amount of an oil microemulsion having an average droplet sizeless than the mean pore size of the sediment, wherein the oilmicroemulsion is formed using an emulsifier and wherein the emulsifieris lecithin, and c) monitoring the aquifer to determine if remediationhas been accomplished.
 41. A method for remediating a selected aquiferin a sediment having a mean pore size to reduce contaminants in theaquifer, comprising: a) evaluating the aquifer for contaminant identityand location, and b) treating the aquifer with a selected amount of anoil microemulsion having an average droplet size less than the mean poresize of the sediment, wherein the oil microemulsion comprises an oilselected from the group consisting of soybean oil, corn oil, canola oil,olive oil, peanut oil, coconut oil, palm oil, rape oil, fish oil, butterand animal tallow, and in which the oil microemulsion acts to stimulatethe growth of microorganisms.
 42. A method for remediating a selectedaquifer in a sediment having a mean pore size to reduce contaminants inthe aquifer, comprising: a) evaluating the aquifer for contaminantidentity and location, and b) treating the aquifer with a selectedamount of an oil microemulsion having an average droplet size less thanthe mean pore size of the sediment, wherein the oil is an edible liquidsoybean oil.
 43. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,comprising: a) evaluating the aquifer for contaminant identity andlocation, and b) treating the aquifer with a selected amount of an oilmicroemulsion having an average droplet size less than the mean poresize of the sediment, wherein the oil microemulsion is formed using anemulsifier, wherein the emulsifier is selected from the group consistingof lecithin, milk solids, carrageenan, guar gum, locust bean gum, karayagum, zanthan gum, pectin, polysorbate, and phosphates.
 44. A method forremediating a selected aquifer in a sediment having a mean pore size toreduce contaminants in the aquifer, comprising: a) evaluating theaquifer for contaminant identity and location, and b) treating theaquifer with a selected amount of an oil microemulsion having an averagedroplet size less than the mean pore size of the sediment, wherein theoil microemulsion is formed using an emulsifier, wherein the emulsifieris lecithin.
 45. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,consisting essentially of treating the aquifer with a selected amount ofan oil microemulsion having an average droplet size less than the meanpore size of the sediment, wherein the oil is an edible liquid soybeanoil.
 46. A method for remediating a selected aquifer in a sedimenthaving a mean pore size to reduce contaminants in the aquifer,consisting essentially of treating the aquifer with a selected amount ofan oil microemulsion having an average droplet size less than the meanpore size of the sediment, wherein the oil microemulsion is formed usingan emulsifier, and wherein the emulsifier is selected from the groupconsisting of lecithin, milk solids, carrageenan, guar gum, locust beangum, karaya gum, zanthan gum, pectin, polysorbate, and phosphates.
 47. Amethod for remediating a selected aquifer in a sediment having a meanpore size to reduce contaminants in the aquifer, consisting essentiallyof treating the aquifer with a selected amount of an oil microemulsionhaving an average droplet size less than the mean pore size of thesediment, wherein the oil microemulsion is formed using an emulsifier,and wherein the emulsifier is lecithin.
 48. A method for remediating aselected aquifer in a sediment having a mean pore size to reducecontaminants in the aquifer, consisting essentially of: (a) evaluatingthe aquifer for contaminant identity and location, (b) treating theaquifer with a selected amount of an oil microemulsion having an averagedroplet size less than the mean pore size of the sediment, wherein theoil microemulsion comprises an oil selected from the group consisting ofsoybean oil, corn oil, canola oil, olive oil, peanut oil, coconut oil,palm oil, rape oil, fish oil, butter and animal tallow, and in which theoil microemulsion acts to stimulate the growth of microorganisms, and(c) monitoring the aquifer to determine if remediation has beenaccomplished.
 49. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,consisting essentially of: a) evaluating the aquifer for contaminantidentity and location, b) treating the aquifer with a selected amount ofan oil microemulsion having an average droplet size less than the meanpore size of the sediment, wherein the oil is an edible liquid soybeanoil, and c) monitoring the aquifer to determine if remediation has beenaccomplished.
 50. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,consisting essentially of: a) evaluating the aquifer for contaminantidentity and location, b) treating the aquifer with a selected amount ofan oil microemulsion having an average droplet size less than the meanpore size of the sediment, wherein the oil microemulsion is formed usingan emulsifier, and wherein the emulsifier is selected from the groupconsisting of lecithin, milk solids, carrageenan, guar gum, locust beangum, karaya gum, zanthan gum, pectin, polysorbate, and phosphates, andc) monitoring the aquifer to determine if remediation has beenaccomplished.
 51. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,consisting essentially of: a) evaluating the aquifer for contaminantidentity and location, b) treating the aquifer with a selected amount ofan oil microemulsion having an average droplet size less than the meanpore size of the sediment, wherein the oil microemulsion is formed usingan emulsifier, wherein the emulsifier is lecithin, and c) monitoring theaquifer to determine if remediation has been accomplished.
 52. A methodfor remediating a selected aquifer in a sediment having a mean pore sizeto reduce contaminants in the aquifer, consisting essentially of: a)evaluating the aquifer for contaminating identity and location, and b)treating the aquifer with a selected amount of an oil microemulsionhaving an average droplet size less than the mean pore size of thesediment, wherein the oil microemulsion comprises an oil selected fromthe group consisting of soybean oil, corn oil, canola oil, olive oil,peanut oil, coconut oil, palm oil, rape oil, fish oil, butter and animaltallow, and in which the oil microemulsion acts to stimulate the growthof microorganisms.
 53. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,consisting essentially of: a) evaluating the aquifer for contaminantidentity and location, and b) treating the aquifer with a selectedamount of an oil microemulsion having an average droplet size less thanthe mean pore size of the sediment, wherein the oil is an edible liquidsoybean oil.
 54. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,consisting essentially of: a) evaluating the aquifer for contaminantidentity and location, and b) treating the aquifer with a selectedamount of an oil microemulsion having an average droplet size less thanthe mean pore size of the sediment, wherein the oil microemulsion isformed using an emulsifier, and wherein the emulsifier is selected fromthe group consisting of lecithin, milk solids, carrageenan, guar gum,locust bean gum, karaya gum, zanthan gum, pectin, polysorbate, andphosphates.
 55. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,consisting essentially of: a) evaluating the aquifer for contaminantidentity and location, and b) treating the aquifer with a selectedamount of an oil microemulsion having an average droplet size less thanthe mean pore size of the sediment, wherein the oil microemulsion isformed using an emulsifier, and wherein the emulsifier is lecithin. 56.A method for remediating a selected aquifer in a sediment having a meanpore size to reduce contaminants in the aquifer, comprising: a)evaluating the aquifer for contaminant identity and location, b)determining whether the aquifer pretreatment should be done, and if so,pretreating the aquifer, c) treating the aquifer with a selected amountof an oil microemulsion having an average droplet size less than themean pore size of the sediment, wherein the oil microemulsion comprisesan oil selected from the group consisting of soybean oil, corn oil,canola oil, olive oil, peanut oil, coconut oil, palm oil, rape oil, fishoil, butter, and animal tallow, and in which the oil microemulsion actsto stimulate the growth of microorganisms, d) determining whetheraquifer post-treatment should be done, and if so, post-treating theaquifer, and e) monitoring the aquifer to determine if remediation hasbeen accomplished.
 57. A method for remediating a selected aquifer in asediment having a mean pore size to reduce contaminants in the aquifer,comprising: a) evaluating the aquifer for contaminant identity andlocation, b) determining whether aquifer pretreatment should be done,and if so, pretreating the aquifer, wherein the pretreatment comprisespretreatment of certain portions of the aquifer with the emulsifierlecithin, c) treating the aquifer with a selected amount of an oilmicroemulsion having an average droplet size less than the mean poresize of the sediment, d) determining whether aquifer post-treatmentshould be done, and if so, post-treating the aquifer, and e) monitoringthe aquifer to determine if remediation has been accomplished.
 58. Amethod for remediating a selected aquifer in a sediment having a meanpore size to reduce contaminants in the aquifer, comprising: a)evaluating the aquifer for contaminant identity and location, b)determining whether aquifer pretreatment should be done, and if so,pretreating the aquifer, c) treating the aquifer with a selected amountof an oil microemulsion having an average droplet size less than themean pore size of the sediment, wherein the oil microemulsion comprisesa food-grade liquid soybean oil, d) determining whether aquiferpost-treatment should be done, and if so, post-treating the aquifer, ande) monitoring the aquifer to determine if remediation has beenaccomplished.